The main function of the intestinal epithelium is to form a selective barrier that protects the host from harmful luminal content while allowing essential nutrients, electrolytes, and water to pass into circulation. Oral exposure to engineered nanomaterials could upset this delicate balance. Nanoparticles are increasingly used in food and food packaging applications and nanoparticles are uniquely reactive with human cells. There is a critical lack of knowledge on how oral exposure to nanoparticles effects small intestinal functionality. Our previous work has shown that oral exposure to polystyrene nanoparticles affects iron absorption. Both in vitro and in vivo, we found that iron absorption was inhibited several hours after exposure to physiologically relevant doses of 50 nm, carboxylated polystyrene nanoparticles. These results demonstrate that there are unexpected physiological consequences to nanoparticle exposure, and the agreement between our in vitro results and in vivo confirmation studies suggests that our in vitro intestinal epithelium model is a powerful tool for high- throughput toxicology screening. The objective of this application is to screen a library of nanoparticles currently used in commercially available food and food packaging to determine the effects of nanoparticle ingestion on small intestinal health and function. This will be accomplished through following specific aims: (1) Examine libraries of engineered nanoparticles commonly found in food and food packaging with an in vitro cell culture model of the GI tract to identify how digestion changes the properties of nanomaterials and how exposure to nanomaterials affects mineral (iron and zinc) absorption. (2) Determine how mineral transporter gene and protein expression, intestinal development, inflammatory activation, and mucus layer composition are affected by nanoparticle exposure. The studies outlined in this application will elucidate the mechanisms by which oral nanoparticle exposure modulates the functionality of the intestinal epithelium. We will determine whether nanoparticles can interfere with the absorption of iron and zinc, two essential minerals. We will establish whether nanoparticle exposure alters gene or protein expression of mineral and nutrient protein transporters or brush border membrane enzymes. We will determine if nanoparticle exposure from food or food packaging at physiologically realistic doses leads to immune activation or reactive oxygen species generation. Finally, we will learn if nanoparticle exposure alters the mucus layer of the gut, which can change mineral and nutrient absorption and GI health and functionality. This valuable information is necessary for health and safety, policy, and regulatory decisions.